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GLPIXELSTORE(3G)		 OpenGL Manual		      GLPIXELSTORE(3G)

NAME
       glPixelStore - set pixel storage modes

C SPECIFICATION
       void glPixelStoref(GLenum pname, GLfloat param);

       void glPixelStorei(GLenum pname, GLint param);

PARAMETERS
       pname
	   Specifies the symbolic name of the parameter to be set. Six values
	   affect the packing of pixel data into memory: GL_PACK_SWAP_BYTES,
	   GL_PACK_LSB_FIRST, GL_PACK_ROW_LENGTH, GL_PACK_IMAGE_HEIGHT,
	   GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS, GL_PACK_SKIP_IMAGES, and
	   GL_PACK_ALIGNMENT. Six more affect the unpacking of pixel data from
	   memory: GL_UNPACK_SWAP_BYTES, GL_UNPACK_LSB_FIRST,
	   GL_UNPACK_ROW_LENGTH, GL_UNPACK_IMAGE_HEIGHT,
	   GL_UNPACK_SKIP_PIXELS, GL_UNPACK_SKIP_ROWS, GL_UNPACK_SKIP_IMAGES,
	   and GL_UNPACK_ALIGNMENT.

       param
	   Specifies the value that pname is set to.

DESCRIPTION
       glPixelStore sets pixel storage modes that affect the operation of
       subsequent glReadPixels() as well as the unpacking of texture patterns
       (see glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(),
       glTexSubImage2D(), glTexSubImage3D()), glCompressedTexImage1D(),
       glCompressedTexImage2D(), glCompressedTexImage3D(),
       glCompressedTexSubImage1D(), glCompressedTexSubImage2D() or
       glCompressedTexSubImage1D().

       pname is a symbolic constant indicating the parameter to be set, and
       param is the new value. Six of the twelve storage parameters affect how
       pixel data is returned to client memory. They are as follows:

       GL_PACK_SWAP_BYTES
	   If true, byte ordering for multibyte color components, depth
	   components, or stencil indices is reversed. That is, if a four-byte
	   component consists of bytes b 0, b 1, b 2, b 3, it is stored in
	   memory as b 3, b 2, b 1, b 0 if GL_PACK_SWAP_BYTES is true.
	   GL_PACK_SWAP_BYTES has no effect on the memory order of components
	   within a pixel, only on the order of bytes within components or
	   indices. For example, the three components of a GL_RGB format pixel
	   are always stored with red first, green second, and blue third,
	   regardless of the value of GL_PACK_SWAP_BYTES.

       GL_PACK_LSB_FIRST
	   If true, bits are ordered within a byte from least significant to
	   most significant; otherwise, the first bit in each byte is the most
	   significant one.

       GL_PACK_ROW_LENGTH
	   If greater than 0, GL_PACK_ROW_LENGTH defines the number of pixels
	   in a row. If the first pixel of a row is placed at location p in
	   memory, then the location of the first pixel of the next row is
	   obtained by skipping

	   k = n ⁢ l a s ⁢ s ⁢ n ⁢ l a ⁢ s >= a s < a

	   components or indices, where n is the number of components or
	   indices in a pixel, l is the number of pixels in a row
	   (GL_PACK_ROW_LENGTH if it is greater than 0, the width argument to
	   the pixel routine otherwise), a is the value of GL_PACK_ALIGNMENT,
	   and s is the size, in bytes, of a single component (if a < s, then
	   it is as if a = s). In the case of 1-bit values, the location of
	   the next row is obtained by skipping

	   k = 8 ⁢ a ⁢ n ⁢ l 8 ⁢ a

	   components or indices.

	   The word component in this description refers to the nonindex
	   values red, green, blue, alpha, and depth. Storage format GL_RGB,
	   for example, has three components per pixel: first red, then green,
	   and finally blue.

       GL_PACK_IMAGE_HEIGHT
	   If greater than 0, GL_PACK_IMAGE_HEIGHT defines the number of
	   pixels in an image three-dimensional texture volume, where
	   ``image'' is defined by all pixels sharing the same third dimension
	   index. If the first pixel of a row is placed at location p in
	   memory, then the location of the first pixel of the next row is
	   obtained by skipping

	   k = n ⁢ l ⁢ h a s ⁢ s ⁢ n ⁢ l ⁢ h a ⁢ s >= a s < a

	   components or indices, where n is the number of components or
	   indices in a pixel, l is the number of pixels in a row
	   (GL_PACK_ROW_LENGTH if it is greater than 0, the width argument to
	   glTexImage3D() otherwise), h is the number of rows in a pixel image
	   (GL_PACK_IMAGE_HEIGHT if it is greater than 0, the height argument
	   to the glTexImage3D() routine otherwise), a is the value of
	   GL_PACK_ALIGNMENT, and s is the size, in bytes, of a single
	   component (if a < s, then it is as if a = s).

	   The word component in this description refers to the nonindex
	   values red, green, blue, alpha, and depth. Storage format GL_RGB,
	   for example, has three components per pixel: first red, then green,
	   and finally blue.

       GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS, and GL_PACK_SKIP_IMAGES
	   These values are provided as a convenience to the programmer; they
	   provide no functionality that cannot be duplicated simply by
	   incrementing the pointer passed to glReadPixels(). Setting
	   GL_PACK_SKIP_PIXELS to i is equivalent to incrementing the pointer
	   by i ⁢ n components or indices, where n is the number of components
	   or indices in each pixel. Setting GL_PACK_SKIP_ROWS to j is
	   equivalent to incrementing the pointer by j ⁢ m components or
	   indices, where m is the number of components or indices per row, as
	   just computed in the GL_PACK_ROW_LENGTH section. Setting
	   GL_PACK_SKIP_IMAGES to k is equivalent to incrementing the pointer
	   by k ⁢ p, where p is the number of components or indices per image,
	   as computed in the GL_PACK_IMAGE_HEIGHT section.

       GL_PACK_ALIGNMENT
	   Specifies the alignment requirements for the start of each pixel
	   row in memory. The allowable values are 1 (byte-alignment), 2 (rows
	   aligned to even-numbered bytes), 4 (word-alignment), and 8 (rows
	   start on double-word boundaries).

       The other six of the twelve storage parameters affect how pixel data is
       read from client memory. These values are significant for
       glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(),
       glTexSubImage2D(), and glTexSubImage3D()

       They are as follows:

       GL_UNPACK_SWAP_BYTES
	   If true, byte ordering for multibyte color components, depth
	   components, or stencil indices is reversed. That is, if a four-byte
	   component consists of bytes b 0, b 1, b 2, b 3, it is taken from
	   memory as b 3, b 2, b 1, b 0 if GL_UNPACK_SWAP_BYTES is true.
	   GL_UNPACK_SWAP_BYTES has no effect on the memory order of
	   components within a pixel, only on the order of bytes within
	   components or indices. For example, the three components of a
	   GL_RGB format pixel are always stored with red first, green second,
	   and blue third, regardless of the value of GL_UNPACK_SWAP_BYTES.

       GL_UNPACK_LSB_FIRST
	   If true, bits are ordered within a byte from least significant to
	   most significant; otherwise, the first bit in each byte is the most
	   significant one.

       GL_UNPACK_ROW_LENGTH
	   If greater than 0, GL_UNPACK_ROW_LENGTH defines the number of
	   pixels in a row. If the first pixel of a row is placed at location
	   p in memory, then the location of the first pixel of the next row
	   is obtained by skipping

	   k = n ⁢ l a s ⁢ s ⁢ n ⁢ l a ⁢ s >= a s < a

	   components or indices, where n is the number of components or
	   indices in a pixel, l is the number of pixels in a row
	   (GL_UNPACK_ROW_LENGTH if it is greater than 0, the width argument
	   to the pixel routine otherwise), a is the value of
	   GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a single
	   component (if a < s, then it is as if a = s). In the case of 1-bit
	   values, the location of the next row is obtained by skipping

	   k = 8 ⁢ a ⁢ n ⁢ l 8 ⁢ a

	   components or indices.

	   The word component in this description refers to the nonindex
	   values red, green, blue, alpha, and depth. Storage format GL_RGB,
	   for example, has three components per pixel: first red, then green,
	   and finally blue.

       GL_UNPACK_IMAGE_HEIGHT
	   If greater than 0, GL_UNPACK_IMAGE_HEIGHT defines the number of
	   pixels in an image of a three-dimensional texture volume. Where
	   ``image'' is defined by all pixel sharing the same third dimension
	   index. If the first pixel of a row is placed at location p in
	   memory, then the location of the first pixel of the next row is
	   obtained by skipping

	   k = n ⁢ l ⁢ h a s ⁢ s ⁢ n ⁢ l ⁢ h a ⁢ s >= a s < a

	   components or indices, where n is the number of components or
	   indices in a pixel, l is the number of pixels in a row
	   (GL_UNPACK_ROW_LENGTH if it is greater than 0, the width argument
	   to glTexImage3D() otherwise), h is the number of rows in an image
	   (GL_UNPACK_IMAGE_HEIGHT if it is greater than 0, the height
	   argument to glTexImage3D() otherwise), a is the value of
	   GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a single
	   component (if a < s, then it is as if a = s).

	   The word component in this description refers to the nonindex
	   values red, green, blue, alpha, and depth. Storage format GL_RGB,
	   for example, has three components per pixel: first red, then green,
	   and finally blue.

       GL_UNPACK_SKIP_PIXELS and GL_UNPACK_SKIP_ROWS
	   These values are provided as a convenience to the programmer; they
	   provide no functionality that cannot be duplicated by incrementing
	   the pointer passed to glTexImage1D(), glTexImage2D(),
	   glTexSubImage1D() or glTexSubImage2D(). Setting
	   GL_UNPACK_SKIP_PIXELS to i is equivalent to incrementing the
	   pointer by i ⁢ n components or indices, where n is the number of
	   components or indices in each pixel. Setting GL_UNPACK_SKIP_ROWS to
	   j is equivalent to incrementing the pointer by j ⁢ k components or
	   indices, where k is the number of components or indices per row, as
	   just computed in the GL_UNPACK_ROW_LENGTH section.

       GL_UNPACK_ALIGNMENT
	   Specifies the alignment requirements for the start of each pixel
	   row in memory. The allowable values are 1 (byte-alignment), 2 (rows
	   aligned to even-numbered bytes), 4 (word-alignment), and 8 (rows
	   start on double-word boundaries).

       The following table gives the type, initial value, and range of valid
       values for each storage parameter that can be set with glPixelStore.

       ┌──────────────────────────────┬──────────────────────────────┬─────────────────────────────────┬───────────────────────────────┐
       │			      │				     │				       │			       │
       │			pname │				Type │			       Initial │			 Valid │
       │			      │				     │ Value			       │ Range			       │
       │			      │				     │				       │			       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_SWAP_BYTES	      │		  boolean	     │		    false	       │	 true or false	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_LSB_FIRST	      │		  boolean	     │		    false	       │	 true or false	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_ROW_LENGTH	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_IMAGE_HEIGHT	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_SKIP_ROWS	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_SKIP_PIXELS	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_SKIP_IMAGES	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_PACK_ALIGNMENT	      │		  integer	     │		      4		       │	 1, 2, 4, or 8	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_SWAP_BYTES	      │		  boolean	     │		    false	       │	 true or false	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_LSB_FIRST	      │		  boolean	     │		    false	       │	 true or false	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_ROW_LENGTH	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_IMAGE_HEIGHT	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_SKIP_ROWS	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_SKIP_PIXELS	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_SKIP_IMAGES	      │		  integer	     │		      0		       │	       0	       │
       ├──────────────────────────────┼──────────────────────────────┼─────────────────────────────────┼───────────────────────────────┤
       │GL_UNPACK_ALIGNMENT	      │		  integer	     │		      4		       │	 1, 2, 4, or 8	       │
       └──────────────────────────────┴──────────────────────────────┴─────────────────────────────────┴───────────────────────────────┘

       glPixelStoref can be used to set any pixel store parameter. If the
       parameter type is boolean, then if param is 0, the parameter is false;
       otherwise it is set to true. If pname is a integer type parameter,
       param is rounded to the nearest integer.

       Likewise, glPixelStorei can also be used to set any of the pixel store
       parameters. Boolean parameters are set to false if param is 0 and true
       otherwise.

ERRORS
       GL_INVALID_ENUM is generated if pname is not an accepted value.

       GL_INVALID_VALUE is generated if a negative row length, pixel skip, or
       row skip value is specified, or if alignment is specified as other than
       1, 2, 4, or 8.

ASSOCIATED GETS
       glGet() with argument GL_PACK_SWAP_BYTES

       glGet() with argument GL_PACK_LSB_FIRST

       glGet() with argument GL_PACK_ROW_LENGTH

       glGet() with argument GL_PACK_IMAGE_HEIGHT

       glGet() with argument GL_PACK_SKIP_ROWS

       glGet() with argument GL_PACK_SKIP_PIXELS

       glGet() with argument GL_PACK_SKIP_IMAGES

       glGet() with argument GL_PACK_ALIGNMENT

       glGet() with argument GL_UNPACK_SWAP_BYTES

       glGet() with argument GL_UNPACK_LSB_FIRST

       glGet() with argument GL_UNPACK_ROW_LENGTH

       glGet() with argument GL_UNPACK_IMAGE_HEIGHT

       glGet() with argument GL_UNPACK_SKIP_ROWS

       glGet() with argument GL_UNPACK_SKIP_PIXELS

       glGet() with argument GL_UNPACK_SKIP_IMAGES

       glGet() with argument GL_UNPACK_ALIGNMENT

SEE ALSO
       glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(),
       glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D(),
       glCompressedTexImage1D(), glCompressedTexImage2D(),
       glCompressedTexImage3D(), glCompressedTexSubImage1D(),
       glCompressedTexSubImage2D(), glCompressedTexSubImage1D().

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc.  © 2011 Khronos Group.
       This document is licensed under the SGI Free Software B License. For
       details, see http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org			  03/16/2013		      GLPIXELSTORE(3G)

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